1. Field of the Invention
The present invention relates generally to a dispensing arrangement for fast food beverages such as milkshakes and similar drinks having a tendency to froth, and more particularly pertains to a dispenser of the aforementioned kind which delivers a precisely quantified portion of such beverages on a controlled and repetitive basis.
2. Discussion of the Prior Art
Many types of arrangements are known in the prior art for dispensing fast food beverages such as milkshakes and similar drinks. The dispensing arrangements normally have a dispensing nozzle and a valve associated therewith for controlling the dispensing operation. Manually controlled dispensing arrangements, wherein an operator manually controls the dispensing vavle, have some serious disadvantages associated therewith. The operator should maintain the dispensing valve open for a sufficient time period to provide or serve the correct quantity of beverage in each cup. The delivery of too little a quantity of a beverage such as a milkshake results in the customer not receiving the amount he paid for, and often results in customer dissatisfaction. On the other hand, the venting of too large a quantity of beverage results in the retail fast food establishment loosing a certain amount of profit on that sale.
One approach employed by the prior art to solve this problem is to mark or emboss a line on the cup at a "full" position. This approach requires the close attention of the dispensing attendant during the dispensing operation, and most often results in the operator overfilling the cup, either because of his slow reaction time or simply because of a lack of attention to duty. The relatively high volume of such dispensing operations in a typical fast food retail outlet translates into a considerable loss of profit for the establishment. Moreover, the detection of the beverage in relationship to the full line is often very difficult to perceive because of the large amount of froth which typically obscures the line prior to the level of the liquid milkshake actually reaching it.
A further disadvantage of this prior art approach is that the dispensing attendant is required to devote his full attention to the dispensing operation, and thus is not free to accomplish other chores, such as the filling of other portions of a customer's order.
It would be extremely desirable to have a dispensing arrangement which automatically provides an accurately dispensed quantity of a beverage such as a milkshake. The prior art is replete with many arrangements for detecting the dispensing of a given quantity of a liquid into a bottle by directing a light beam across the neck of the bottle at a full position location and detecting the interruption of the light beam by the rising liquid in the bottle. A simple approach of this nature has some serious drawbacks and disadvantages when a frothy type of liquid is being dispensed, as the froth on top of the liquid tends to obscure the light beam prior to the liquid level reaching a full position, and thus often results in erroneous and inaccurate quantities of liquid being dispensed. This can be a relatively severe problem as the profits from this type of retail business are often related directly to the dispensing of an accurate quantity or portion on a repetitive baiss.
Calhoun U.S. Pat. No. 3,454,759 is of interest to the present invention by disclosing a system for detecting the level of a liquid in a container even when froth or foam is present thereabove. The system directs a light beam with frequencies in both the visible and infrared bands towards the container at substantially the level to be measured. The container passes the light in the visible and infrared bands. The liquid in the container passes the light in the visible band but attenuates the light in the infrared band, while the foam thereabove attenuates the light in both the visible and infrared bands. The light passing from the container is filtered such that only light in the infrared band is passed to an infrared cell. When the infrared cell continuously produced a signal of relatively low amplitude, an indication is provided that neither the liquid or the foam above the liquid has reached the desired level. A second detector cell receives the visible light passing from the container. When this cell produces a signal of relatively high amplitude, an indication is provided that the foam above the liquid is not yet at the desired level. In this way, circuitry associated with the infrared and second detector cells provides an indication as to the level of the liquid in the container which is not rendered inaccurate by the foam thereabove. This prior art arrangement is relatively complicated when compared with the simple and straightforward approach of the present invention.
Upton U.S. Pat. No. 4,202,387 is also of interest to the subject invention by providing a beverage dispensing control system in which a signal is generated which indicates the size of the container to be filled. Valve control timer means, responsive to this selection signal, opens a dispensing valve for the correct duration of time required to fill a container of the indicated size. The container size is sensed by a set of photosensors and associated light sources that are mounted on the dispenser housing beneath the spout. Each light source/photosensor assembly is located at a position appropriate to sense a container of a given size. When the container is placed on the base of the dispenser housing, light is reflected from one or more of the light source back into the associated photosensors. Discrimination circuitry associated with the photosensors then establishes the size of the container, depending on which of the photosensors detects the reflected light. This patent utilizes reflected light to detect different size containers, and does not utilize light transmitted through the top and one side of a container to provide an accurate measurement of the dispensed liquid despite froth or foam on top thereof.